Manage insecticide use for soybean aphids carefully

ST. PAUL, Minn. (7/21/2016) — Science-based approaches to controlling soybean aphid numbers should be carefully integrated to maximize profitability for soybean farmers. An integrated pest management (IPM) approach minimizes the aphid’s impact on soybean yields and helps prevent insecticide resistance.
This week, University of Minnesota Extension crop science faculty led a multi-state effort in issuing a white paper to remind the agricultural community when insecticides are an appropriate response to soybean aphids—and when they’re unnecessary and even potentially harmful. Research-driven recommendations, they added, prolong the life of useful management tools.

“Importantly, long-term returns can be reduced if insecticide resistance becomes fixed in the soybean aphid population. This has happened many, many times in the history of pest management. We know that managing pesticide-resistant pests is seldom cheap and easy,” wrote Extension’s Bruce Potter, integrative pest management specialist, Phil Glogoza, educator, and Bob Koch, entomologist. They were joined by 13 peers from nine other land-grant universities.

Their review of effective pest management principles is available at “Just the facts: A review of the biology and economics behind soybean aphid insecticide recommendations,” also viewable at z.umn.edu/aphidmgt. Management recommendations are based on a 250-aphids-per-plant economic threshold for treatment.

“We’re seeing some growers spraying crops when it’s not needed,” Glogoza said. “In addition to the worrisome prospect of aphids developing resistance to insecticides, we’re also concerned about insecticide killing beneficial insects and other negative impacts.”

The researchers also warned against using crop or product prices as a reason to apply insecticide: “The insects on your farm do not eat faster or more when crop prices are high or insecticide costs are low; nor is your crop more sensitive to insect damage,” they wrote. “It makes no sense to treat if there is no reasonable likelihood of damage.”

Resistance to insecticides and other pest control chemicals has emerged as a leading agricultural concern. As pest populations become more resistant to a pesticide, the pesticide becomes increasingly less effective. It can reach a point where, along with other related chemicals, it’s basically lost as a tool for managing that pest.

University of Minnesota Extension collaborated on this effort with colleagues from Iowa State University, Purdue University, Pennsylvania State University, Michigan State University, Ohio State University, North Dakota State University, University of Nebraska and University of Illinois.

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